The inhibitory effects of carnosic acid on cervical cancer cells growth by promoting apoptosis via ROS-regulated signaling pathway

Carnosic acid: an effective phenolic diterpenoid for prevention and management of cancers via targeting multiple signaling pathways

Cancer is a serious global public health issue, and a great deal of research has been made to treat cancer. Of these, discovery of promising compounds that effectively fight cancer always has been the main point of interest in pharmaceutical research. Carnosic acid (CA) is a phenolic diterpenoid compound widely present in Lamiaceae plants such as Rosemary (Rosmarinus officinalis L.). In recent years, there has been increasing evidence that CA has significant anti-cancer activity, such as leukaemia, colorectal cancer, breast cancer, lung cancer, liver cancer, pancreatic cancer, stomach cancer, lymphoma, prostate cancer, oral cancer, etc. The potential mechanisms involved by CA, including inhibiting cell proliferation, inhibiting metastasis, inducing cell apoptosis, stimulating autophagy, regulating the immune system, reducing inflammation, regulating the gut microbiota, and enhancing the effects of other anti-cancer drugs. This article reviews the biosynthesis, pharmacokinetics and metabolism, safety and toxicity, as well as the molecular mechanisms and signaling pathways of the anticancer activity of CA. This will contribute to the development of CA or CA-containing functional foods for the prevention and treatment of cancer, providing important advances in the advancement of cancer treatment strategies.

Anticancer diterpenes of African natural products: Mechanistic pathways and preclinical developments

BACKGROUND

The African continent is home to five biodiversity hotspots, boasting an immense wealth of medicinal flora, fungi and marine life. Diterpenes extracted from such natural products have compelling cytotoxic activities that warrant further exploration for the drug market, particularly in cancer therapy, where mortality rates remain elevated worldwide.

PURPOSE

To demonstrate the potential of African natural products on the global stage for cancer therapy development and provide an in-depth analysis of the current literature on the activity of cancer cytotoxic diterpenes from African natural sources (to our knowledge, the first of its kind); not only to reveal the most promising candidates for clinical development, but to demonstrate the importance of preserving the threatened ecosystems of Africa.

METHODS

A comprehensive search by means of the PRISMA strategy was conducted using electronic databases, namely Web of Science, PubMed, Google Scholar and ScienceDirect. The search terms employed were 'diterpene & mechanism & cancer' and 'diterpene & clinical & cancer'. The selection process involved assessing titles in English, Portuguese and Spanish, adhering to predefined eligibility criteria. The timeframe for inclusion spanned from 2010 to 2023, resulting in 218 relevant papers. Chemical structures were visualized using ChemDraw 21.0, PubChem was utilized to search for CID numbers.

RESULTS

Despite being one of the richest biodiverse zones in the world, African natural products are proportionally underreported compared to Asian countries or otherwise. The diterpenes andrographolide (Andrographis paniculata), forskolin (Coleus forskohlii), ent-kauranes from Isodon spp., euphosorophane A (Euphorbia sororia), cafestol & kahweol (Coffea spp.), macrocylic jolkinol D derivatives (Euphorbia piscatoria) and cyathane erinacine A (Hericium erinaceus) illustrated the most encouraging data for further cancer therapy exploration and development.

CONCLUSIONS

Diterpenes from African natural products have the potential to be economically significant active pharmaceutical and medicinal ingredients, specifically focussed on anticancer therapeutics.

Carnosic Acid against Lung Cancer: Induction of Autophagy and Activation of Sestrin-2/LKB1/AMPK Signalling

Non-small cell lung cancer (NSCLC) represents 80% of all lung cancer cases and is characterized by low survival rates due to chemotherapy and radiation resistance. Novel treatment strategies for NSCLC are urgently needed. Liver kinase B1 (LKB1), a tumor suppressor prevalently mutated in NSCLC, activates AMP-activated protein kinase (AMPK) which in turn inhibits mammalian target of rapamycin complex 1 (mTORC1) and activates unc-51 like autophagy activating kinase 1 (ULK1) to promote autophagy. Sestrin-2 is a stress-induced protein that enhances LKB1-dependent activation of AMPK, functioning as a tumor suppressor in NSCLC. In previous studies, rosemary (Rosmarinus officinalis) extract (RE) activated the AMPK pathway while inhibiting mTORC1 to suppress proliferation, survival, and migration, leading to the apoptosis of NSCLC cells. In the present study, we investigated the anticancer potential of carnosic acid (CA), a bioactive polyphenolic diterpene compound found in RE. The treatment of H1299 and H460 NSCLC cells with CA resulted in concentration and time-dependent inhibition of cell proliferation assessed with crystal violet staining and 3H-thymidine incorporation, and concentration-dependent inhibition of survival, assessed using a colony formation assay. Additionally, CA induced apoptosis of H1299 cells as indicated by decreased B-cell lymphoma 2 (Bcl-2) levels, increased cleaved caspase-3, -7, poly (ADP-ribose) polymerase (PARP), Bcl-2-associated X protein (BAX) levels, and increased nuclear condensation. These antiproliferative and proapoptotic effects coincided with the upregulation of sestrin-2 and the phosphorylation/activation of LKB1 and AMPK. Downstream of AMPK signaling, CA increased levels of autophagy marker light chain 3 (LC3), an established marker of autophagy; inhibiting autophagy with 3-methyladenine (3MA) blocked the antiproliferative effect of CA. Overall, these data indicate that CA can inhibit NSCLC cell viability and that the underlying mechanism of action of CA involves the induction of autophagy through a Sestrin-2/LKB1/AMPK signaling cascade. Future experiments will use siRNA and small molecule inhibitors to better elucidate the role of these signaling molecules in the mechanism of action of CA as well as tumor xenograft models to assess the anticancer properties of CA in vivo.

Exploring the Potential of Rosemary Derived Compounds (Rosmarinic and Carnosic Acids) as Cancer Therapeutics: Current Knowledge and Future Perspectives

Cancer is a global health challenge with high morbidity and mortality rates. However, conventional cancer treatment methods often have severe side effects and limited success rates. In the last decade, extensive research has been conducted to develop safe, and efficient alternative treatments that do not have the limitations of existing anticancer medicines. Plant-derived compounds have shown promise in cancer treatment for their anti-carcinogenic and anti-proliferative properties. Rosmarinic acid (RA) and carnosic acid (CA) are potent polyphenolic compounds found in rosemary (Rosmarinus officinalis) extract. They have been extensively studied for their biological properties, which include anti-diabetic, anti-inflammatory, antioxidant, and anticancer activities. In addition, RA and CA have demonstrated effective anti-proliferative properties against various cancers, making them promising targets for extensive research to develop candidate or leading compounds for cancer treatment. This review discusses and summarizes the anti-tumor effect of RA and CA against various cancers and highlights the involved biochemical and mechanistic pathways.

Advances on Natural Abietane, Labdane and Clerodane Diterpenes as Anti-Cancer Agents: Sources and Mechanisms of Action

Extensive research over the past decades has identified numerous phytochemicals that could represent an important source of anti-cancer compounds. There is an immediate need for less toxic and more effective preventive and therapeutic strategies for the treatment of cancer. Natural compounds are considered suitable candidates for the development of new anti-cancer drugs due to their pleiotropic actions on target events with multiple manners. This comprehensive review highlighted the most relevant findings achieved in the screening of phytochemicals for anticancer drug development, particularly focused on a promising class of phytochemicals such as diterpenes with abietane, clerodane, and labdane skeleton. The chemical structure of these compounds, their main natural sources, and mechanisms of action were critically discussed.

Induction of ferroptosis by carnosic acid-mediated inactivation of Nrf2/HO-1 potentiates cisplatin responsiveness in OSCC cells

Oral squamous cell carcinoma (OSCC) represents an increasing problem in the global public health due to the high incidence and worsening prognosis. Traditional chemotherapy extends the limited benefit for OSCC patients because of acquired drug resistance. Carnosic acid is an important polyphenol and has attracted more interesting based on the indispensable role in the progression of several cancers. Nevertheless, its roles in OSCC remain elusive. In this study, carnosic acid dose-dependently inhibited OSCC cell viability while preserving normal oral keratinocytes. Importantly, carnosic acid application sensitised cisplatin-resistant CAL27-DDP and SCC9-DDP cells to cisplatin by decreasing cell viability and increasing cell death. Noticeably, SCC9-DDP and CAL27-DDP cells exhibited lower ferroptosis relative to the parental cells evident by the higher intracellular GSH levels and lower ROS and lipid peroxidation in cisplatin-resistant cells. Treatment with carnosic acid induced ferroptosis in cisplatin-resistant OSCC cells; however, this suppression was reversed following the application of ferroptosis antagonist liproxstatin-1 (Lip-1), indicating the involvement of ferroptosis for carnosic acid-mediated cisplatin resistance. Furthermore, compared with parental cells, stronger activation of the Nrf2/HO-1/xCT signaling was observed in cisplatin-resistant cells, which was inhibited by carnosic acid. Of interest, reactivating the Nrf2 signaling reversed carnosic acid-evoked ferroptosis in cisplatin-resistant cells and ultimately attenuated carnosic acid-mediated cell sensitivity to cisplatin. Together, the current findings highlight that carnosic acid may re-sensitize cisplatin-resistant cells to cisplatin by inducing ferroptosis, which involves the inactivation of Nrf2/HO-1/xCT pathway. Hence, this research may support a promising therapeutic approach to overcome chemoresistance in OSCC.

Natural Bioactives: Back to the Future in the Fight against Human Papillomavirus? A Narrative Review

Human papillomavirus (HPV) still represents an important threat to health worldwide. Better therapy in terms of further improvement of outcomes and attenuation of related side-effects is desirable. The pharmaceutical industry has always targeted natural substances-phytochemicals in particular-to identify lead compounds to be clinically validated and industrially produced as antiviral and anticancer drugs. In the field of HPV, numerous naturally occurring bioactives and dietary phytochemicals have been investigated as potentially valuable in vitro and in vivo. Interference with several pathways and improvement of the efficacy of chemotherapeutic agents have been demonstrated. Notably, some clinical trials have been conducted. Despite being endowed with general safety, these natural substances are in urgent need of further assessment to foresee their clinical exploitation. This review summarizes the basic research efforts conducted so far in the study of anti-HPV properties of bio-actives with insights into their mechanisms of action and highlights the variety of their natural origin in order to provide comprehensive mapping throughout the different sources. The clinical studies available are reported, as well, to highlight the need of uniformity and consistency of studies in the future to select those natural compounds that may be suited to clinical application.

Phytocompounds from the medicinal and dietary plants: Multi-target agents for cancer prevention and therapy

Cervical cancer is the fourth leading cause of cancer death among women worldwide. Due to cervical cancer's high incidence and mortality, there is an unmet demand for effective diagnostic, therapeutic, and preventive agents. At present, the preferred treatment strategies for advanced metastatic cervical cancer include surgery, radiotherapy, and chemotherapy. However, cervical cancer is gradually developing resistance to chemotherapy, thereby reducing its efficacy. Over the last several decades, phytochemicals, a general term for compounds produced from plants, have gained attention for their role in preventing cervical cancer. This role in cervical cancer prevention has garnered attention on the medicinal properties of fruits and vegetables. Phytochemicals are currently being evaluated for their ability to block proteins involved in carcinogenesis and chemoresistance against cervical cancer. Chemoresistance to cancer drugs like cisplatin, doxorubicin, and 5-fluorouracil has become a significant limitation of drug-based chemotherapy. However, the combination of cisplatin with other phytochemicals has been identified as a promising alternative to subjugate cisplatin resistance. Phytochemicals are promising chemo-preventive and chemotherapeutic agents as they possess antioxidant, anti-inflammatory, and anti-proliferative potential against many cancers, including cervical cancer. Furthermore, the ability of the phytochemicals to modulate cellular signaling pathways through up and down regulation of various proteins has been claimed for their therapeutic potential. Phytochemicals also display a wide range of biological functions, including cell cycle arrest, apoptosis induction, inhibition of invasion, and migration in cervical cancer cells. Numerous studies have revealed the critical role of different signaling proteins and their signaling pathways in the pathogenesis of cervical cancer. Here, we review the ability of several dietary phytochemicals to alter carcinogenesis by modulating various molecular targets.

Curcumin and Carnosic Acid Cooperate to Inhibit Proliferation and Alter Mitochondrial Function of Metastatic Prostate Cancer Cells

Anticancer activities of plant polyphenols have been demonstrated in various models of neoplasia. However, evidence obtained in numerous in vitro studies indicates that proliferation arrest and/or killing of cancer cells require quite high micromolar concentrations of polyphenols that are difficult to reach in vivo and can also be (geno)toxic to at least some types of normal cells. The ability of certain polyphenols to synergize with one another at low concentrations can be used as a promising strategy to effectively treat human malignancies. We have recently reported that curcumin and carnosic acid applied at non-cytotoxic concentrations synergistically cooperate to induce massive apoptosis in acute myeloid leukemia cells, but not in normal hematopoietic and non-hematopoietic cells, via sustained cytosolic calcium overload. Here, we show that the two polyphenols can also synergistically suppress the growth of DU145 and PC-3 metastatic prostate cancer cell cultures. However, instead of cell killing, the combined treatment induced a marked inhibition of cell proliferation associated with G₀/G₁ cell cycle arrest. This was preceded by transient elevation of cytosolic calcium levels and prolonged dissipation of the mitochondrial membrane potential, without generating oxidative stress, and was associated with defective oxidative phosphorylation encompassing mitochondrial dysfunction. The above effects were concomitant with a significant downregulation of mRNA and protein expression of the oncogenic kinase SGK1, the mitochondria-hosted mTOR component. In addition, a moderate decrease in SGK1 phosphorylation at Ser422 was observed in polyphenol-treated cells. The mTOR inhibitor rapamycin produced a similar reduction in SGK1 mRNA and protein levels as well as phosphorylation. Collectively, our findings suggest that the combination of curcumin and carnosic acid at potentially bioavailable concentrations may effectively target different types of cancer cells by distinct modes of action. This and similar combinations merit further exploration as an anticancer modality.

Transferrin-conjugated liposomes loaded with carnosic acid inhibit liver cancer growth by inducing mitochondria-mediated apoptosis

Our previous studies have proven that carnosic acid (CA) induces apoptosis of liver cancer cells. However, the poor chemical properties of CA limit its in vivo anti-cancer effects. In this study, CA was loaded into liposomes (LP-CA), and LP-CA was further conjugated with transferrin (Tf-LP-CA) to overcome the shortcomings of poor solubility and absorption at the lesion site. In HepG2 and SMMC-7721 cells, compared with CA and LP-CA, more Tf-LP-CA was absorbed by liver cancer cells, which induced higher levels of apoptosis and reduced the mitochondrial membrane potential more effectively. In HepG2- and SMMC-7721-xenotransplanted mice, Tf-LP-CA inhibited tumor growth with no cytotoxicity to the liver, spleen, or kidney. Furthermore, compared with CA and LP-CA, Tf-LP-CA targeted the tumor site more effectively, enhanced the expressions of cleaved poly(ADP-ribose) polymerase, and Caspase-3 and -9, and regulated the expression levels of B-cell lymphoma 2 (Bcl2) family members in the tumor tissues. Tf-LP-CA was taken up by tumor cells and targeted at tumor tissues, ensuring the precise delivery of CA, which further promoted mitochondria-mediated intrinsic apoptosis in the liver cancer cells. These results provide evidence for the clinical application of the Tf-LP-based CA drug delivery system for liver cancer.

The Involvement of Natural Polyphenols in the Chemoprevention of Cervical Cancer

From all types of cancer, cervical cancer manages to be in top four most frequent types, with a 6.5% rate of occurrence. The infectious vector that induces the disease, the high-risk Human papillomavirus (HPV), which is a sexually transmitted virus, is capable of transforming the host cell by modulating some of the principal signaling pathways responsible for cell cycle arrest, proliferation, and survival. Fortunately, like other cancer types, cervical cancer can be treated by chirurgical interventions or chemoradiotherapy, but these methods are not exactly the lucky clover of modern medicine because of the adverse effects they have. That is the reason why in the last years the emphasis has been on alternative medicine, more specifically on phytochemicals, as a substantial number of studies showed that diet contributes to cancer prevention and treatment. All these studies are trying to find new chemopreventive agents with less toxicity but high effectiveness both in vitro and in vivo. The aim of this review is to evaluate the literature in order to underline the advantages and disadvantages of polyphenols, a class of dietary compounds, as chemopreventive and chemotherapeutic agents. This review also aims to present polyphenols from different perspectives, starting with mechanisms of action and ending with their toxicity. The bigger picture illustrates that polyphenols have great potential in cervical cancer prevention, with strong effects on gene modulation.

An Overview of Novel Agents for Cervical Cancer Treatment by Inducing Apoptosis: Emerging Drugs Ongoing Clinical Trials and Preclinical Studies

As the leading cause of cancer death, cervical cancer ranks fourth for both incidence and mortality. Cervical cancer incidence and mortality rates have reportedly decreased over the last decades thanks to extensive screening and widespread vaccination against human papilloma virus. However, there have been no major improvements concerning platinum-based chemotherapy on the survival of advanced cervical cancer. Thus, novel agents are urgently needed for the improvement of therapeutic effect. With the development of molecular biology and genomics, targeted therapy research has achieved a breakthrough development, including anti-angiogenesis, immune checkpoint inhibitors, and other treatments that are efficient for treatment of cervical cancer. Apoptosis is a crucial process for tumor progression. Drugs directed at inducing tumor-cell apoptosis are regarded as important treatment modalities. Besides, a number of novel compounds synthesized or derived from plants or microorganisms exhibited prominent anti-cancer activity by changing the apoptotic balance in cervical cancer. In this review, we summarized new target therapy drugs ongoing clinical trials that are used for treatment of cervical cancer. Further, we classified novel agents with a focus on improvement of therapeutic effect pre-clinically. To summarize, we also discussed application prospects of the new uses of old drugs and drug combinations, to provide researchers with new ideas for cervical cancer treatment.

Studies on apoptosis induced by B-norcholesteryl benzimidazole compounds in HeLa cells

Certain B-norcholesteryl benzimidazole compounds were found to mediate marked anti-tumor proliferative effects in vitro in our earlier study. Here, the mechanism of action of these anti-tumor effects was evaluated using HeLa human cervical cancer cells. Methods for detecting cell invasion and migration, Annexin V-PI double staining, cell cycle status, and mitochondrial membrane potential Δψm were employed. These compounds were confirmed to significantly inhibit the proliferation of HeLa cells in vitro. Compound 1 induced apoptosis in S phase, compound 2induced apoptosis in the G0/G1 phase and compound 3 induced late apoptosis in the G2/M phase. These compounds induced HeLa cell apoptosis through depolarization of mitochondrial membrane potential Δψm in a dose-dependent manner. B-norcholesteryl benzimidazole compounds induced morphological changes in HeLa cells and inhibited proliferation, invasion and metastasis. Apoptosis was promoted by mechanisms involving p21 and p53 in this cervical cancer cell line.

Carnosic Acid Induces Apoptosis and Inhibits Akt/mTOR Signaling in Human Gastric Cancer Cell Lines

Gastric cancer is among the most common malignancies worldwide. Due to limited availability of therapeutic options, there is a constant need to find new therapies that could target advanced, recurrent, and metastatic gastric cancer. Carnosic acid is a naturally occurring polyphenolic abietane diterpene derived from Rosmarinus officinalis and reported to have numerous pharmacological effects. In this study, the cytotoxicity assay, Annexin V-FITC/PI, caspases 3, 8, and 9, cell cycle analysis, and Western blotting were used to assess the effect of carnosic acid on the growth and survival of human gastric cancer cell lines (AGS and MKN-45). Our findings showed that carnosic acid inhibited human gastric cancer cell proliferation and survival in a dose-dependent manner. Additionally, carnosic acid is found to inhibit the phosphorylation/activation of Akt and mTOR. Moreover, carnosic acid enhanced the cleavage of PARP and downregulated survivin expression, both being known markers of apoptosis. In conclusion, carnosic acid exhibits antitumor activity against human gastric cancer cells via modulating the Akt-mTOR signaling pathway that plays a crucial role in gastric cancer cell proliferation and survival.

Development of a caffeic acid–phthalimide hybrid compound for NADPH oxidase inhibition

NADPH oxidases are pharmacological targets for the treatment of inflammation-based diseases. This work presents the synthesis and study of a caffeic acid/phthalimide hybrid compound (C2) as a potential inhibitor of NADPH oxidases. Throughout the study, we have compared compound C2 with its precursor caffeic acid (C1). The redox properties were compared using three different antioxidant methodologies and showed that C2 was slightly less effective than C1, a well-established and robust antioxidant. However, C2 was three-fold more effective than albumin (used as a model protein). This chemical feature was decisive for the higher efficiency of C2 as an inhibitor of the release of superoxide anions by stimulated neutrophils and enzymatic activity of cell-free NADPH oxidase. Docking simulation studies were performed using the crystal structure of the recombinant dehydrogenase domain of the isoform NOX5 of C. stagnale, which retains the FAD cofactor (PDB: 5O0X). Considering that C2 could bind at the FAD redox site of NOX5, studies were conducted by comparing the interactions and binding energies of C1 and C2. The binding energies were −50.30 (C1) and −74.88 (C2) (kJ mol⁻¹), which is in agreement with the higher efficacy of the latter as an NADPH oxidase inhibitor. In conclusion, incorporating the phthalimide moiety into caffeic acid was decisive for its effectiveness as an NADPH oxidase inhibitor.

The incorporation of the phthalimide moiety into caffeic acid was decisive for its effectiveness as an NADPH oxidase inhibitor.

Carnosic acid exhibits antiproliferative and proapoptotic effects in tumoral NCI-H460 and nontumoral IMR-90 lung cells

Carnosic acid (CA) is a phenolic diterpene with many important biological activities including antimicrobial, antioxidant, anti-inflammatory properties, and anti-proliferative properties. The aim of the present study was to investigate cytotoxic activity, cell cycle, apoptotic, and molecular effects attributed to CA in non-tumoral IMR-90 (human fetal lung fibroblasts), as well as tumoral NCI-H460 (human non-small-cell lung cancer) cell lines. Cell proliferation was evaluated by Real-Time Cell Analysis system, while apoptosis and cell cycle were assessed using flow cytometry. RT-qPCR was used to estimate the relative expression of genes involved in cell cycle regulation, DNA damage and repair, and apoptosis induction. CA inhibited proliferation of IMR-90 and NCI-H460 cells via cell cycle arrest at G₀/G₁ and G₂/M phases, according to the treatment concentration. The mRNA levels of genes encoding cyclins A2, B1, and B2 were downregulated in response to CA treatment of IMR-90 cells. Apoptosis was induced and proapoptotic gene PUMA was upregulated in both cell lines. mRNA levels of genes ATR, CCND1, CHK1, CHK2, MYC, GADD45A, H2AFX, MTOR, TP53, and BCL2, CASP3 were not markedly changed following CA treatments. Although CA exerted antiproliferative activity against NCI-H460 tumor cells, this phytochemical induced toxic effects in non-tumoral cells, and thus needs to be considered carefully prior to pharmacological use therapeutically.

Mitochondrial respiratory chain dysfunction mediated by ROS is a primary point of fluoride-induced damage in Hepa1-6 cells

To evaluate the mechanism of fluoride (F) mitochondrial toxicity, we cultured Hepa1-6 cells with different F concentrations (0, 1 and 2 mmoL/L) and determined cell pathological morphology, mitochondrial respiratory chain damage and cell cycle change. Results showed that the activities and mRNA expression levels of antioxidant enzymes considerably decreased, whereas the contents of reactive oxygen species (ROS), malondialdehyde (MDA) and nitric oxide (NO) markedly increased. Breakage of mitochondrial cristae and substantial vacuolated mitochondria were observed by transmission electron microscopy. These results indicate the F-induced oxidative damage in Hepa1-6 cells. The enzyme activities of mitochondrial complexes I, II, III and IV were disordered in Hepa1-6 cells treated by excessive F, thereby indicating a remarkable down-regulation. Further research showed that complex subunits also demonstrated the development of disorder, in which the protein expressions levels of NDUFV2 and SDHA were substantially down-regulated, whereas those of CYC1 and COX Ⅳ were markedly up-regulated. Reductions in ATP and mitochondrial membrane potential were detected with the dysfunction of the mitochondrial respiratory chain. The G2/M phase arrest of the cell cycle in Hepa1-6 cells was measured via flow cytometry, and the up-regulated protein expressions of Cyt c, caspase 9, caspase 3 and substantial apoptotic cells were determined. In summary, this study demonstrated that ROS-mediated mitochondrial respiratory chain dysfunction causes F-induced Hepa1-6 cell damage.

Antiproliferative Activity of Carnosic Acid is Mediated via Inhibition of Cell Migration and Invasion, and Suppression of Phosphatidylinositol 3-Kinases (PI3K)/AKT/Mammalian Target of Rapamycin (mTOR) Signaling Pathway

BACKGROUND Lung cancer is one of the leading causes of cancer-related mortalities worldwide and majority of these deaths result from non-small cell lung cancer (NSCLC). The primary objective of this research was to determine the anticancer potential of carnosic acid, a plant derived abietane diterpene, against human lung cancer cells, as well as to determine its effects on cell migration and invasion, apoptosis, and the PI3K/AKT/m-TOR signaling pathway. MATERIAL AND METHODS Cell viability was evaluated by Cell Counting Kit-8 (CCK-8) assay; fluorescence microscopy using acridine orange/ethidium bromide stain and Comet assay were used to study cellular apoptosis. In vitro wound healing assay was used to study effects on cell migration; Transwell assay was used to study cell invasion after drug treatment. Western blot assay was used to study effects of carnosic acid on the PI3K/AKT/m-TOR signaling pathway. RESULTS It was shown that carnosic acid could inhibit the growth of A-549 human non-small cell lung carcinoma cells dose-dependently showing an IC₅₀ value of 12.5 μM. This growth inhibition of A-549 cells was mediated via apoptotic cell death as observed by fluorescence microscopy showing nuclear fragmentation and chromatin condensation. Carnosic acid, dose-dependently, also inhibited cell migration and invasion. Finally, western blot assay revealed that carnosic acid also led to inhibition of the PI3K/AKT/m-TOR signaling pathway. CONCLUSIONS In conclusion, our results showed that Carnosic acid has the potential to inhibit cancer cell growth in A-549 lung cancer cells by activating apoptotic death, inhibiting cell migration and invasion and suppressing PI3K/AKT/m-TOR signaling pathway.

Intelectin mediated phagocytosis and killing activity of macrophages in blunt snout bream (Megalobrama amblycephala)

Intelectin, a lectin discovered recently, has been identified in various vertebrate species, such as fish, amphibians, and mammals. In one of our previous studies, the efficient bacteria binding and agglutinating activity of the recombinant Megalobrama amblycephala intelectin protein (rMamINTL) and the enhanced immunopositive localization have been observed in the hepatic macrophage-like cells (kupffer cells) post Aeromonas hydrophila infection. Thus, the present study primarily focuses on the regulatory effects of rMamINTL on M. amblycephala macrophages. This study revealed a prominent LPS-binding activity of rMamINTL and a significantly increased phagocytosis of rMamINTL-treated A. hydrophila by M. amblycephala macrophages. However, the rMamINTL-treated M. amblycephala macrophages exhibited no evident regulatory effect on phagocytosis, whereas the enhanced killing activity of the rMamINTL-treated macrophages was observed, which may be attributed to the induced respiratory burst activity and the expression of inflammatory cytokines. In addition, the anti-proliferation effect of rMamINTL on two tumor cells was observed. However, its mechanism remains to be further studied. In short, these results show that MamINTL is a multifunctional immune protein with effective immunomodulatory activity.

Carnosic acid potentiates the anticancer effect of temozolomide by inducing apoptosis and autophagy in glioma

OBJECTIVE

Malignant glioma is a lethal brain tumor with a low survival rate and poor prognosis. New strategies are urgently needed to augment the chemotherapeutic effects of temozolomide (TMZ), the standard drug in glioma treatment. Carnosic acid (CA) has been reported to have anticancer, antioxidant and anti-infectious properties. In this study, we aimed to investigate the anticancer effects and the underlying mechanisms of CA in combination with TMZ in glioma cancer cells.

METHODS

The glioma cancer cells were treated with TMZ, CA, or TMZ + CA. We evaluated cell survival by CCK-8 assay, cell anchorage-independent survival by colony formation assay, cell migration by wound-healing assay, cell cycle and cell apoptosis by flow cytometry, and protein expression by western blot.

RESULTS

CA enhanced the cytotoxic effect of TMZ in glioma cancer cells. CA enhanced TMZ-induced inhibition of colony formation and cell migration and enhanced TMZ-induced cell cycle arrest and cellular apoptosis. Immunofluorescence suggested that CA in combination with TMZ triggered autophagy. Furthermore, CA promoted TMZ-induced cell cycle arrest and cellular apoptosis by Cyclin B1 inhibition and activation of PARP and Caspase-3, while CA promoted TMZ-induced cellular autophagy by p-AKT inhibition, p62 downregulation and LC3-I to LC3-II transition.

CONCLUSION

These data suggest that the combination therapy of CA and TMZ strengthens the anticancer effect of TMZ by enhancing apoptosis and autophagy.

Selenium Antagonizes the Lead-Induced Apoptosis of Chicken Splenic Lymphocytes In Vitro by Activating the PI3K/Akt Pathway

Lead (Pb) pollution has become one of the most serious global ecological problems. In animals, Pb ingestion induces apoptosis in many tissues. However, the mechanisms by which Pb induces apoptosis in chicken splenic lymphocytes in vitro via the PI3K/Akt pathway and the antagonistic effect of selenium (Se) on Pb remain unclear. Therefore, we established the in vitro Se-Pb interaction model in chicken splenic lymphocytes and examined the frequency of apoptotic cells using acridine orange/ethidium bromide (AO/EB) staining and the TdT-mediated dUTP nick end labeling assay and detected the activities of glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT), as well as the levels of malondialdehyde (MDA) and reactive oxygen species (ROS). The expression of PI3K/Akt pathway-related genes was also examined by qRT-PCR and western blotting. MDA and ROS levels were markedly increased, whereas the activities of GPx, SOD, and CAT were significantly decreased; the levels of the PI3K, Akt, and Bcl-2 messenger RNAs (mRNAs) and proteins were decreased; and the levels of the p53, Bax, cytochrome c (Cyt-c), caspase 3, and caspase 9 mRNAs and proteins were increased in the Pb group. In addition, the frequency of apoptotic cells was also significantly increased by the Pb treatment. However, Se supplementation during Pb exposure observably attenuated Pb-induced apoptosis; increased the levels of the PI3K, Akt, and Bcl-2 mRNAs and proteins; and decrease the levels of the p53, Bax, Cyt-c, caspase 3, and caspase 9 mRNAs and proteins in the chicken spleen. In conclusion, Pb exposure causes oxidative stress, inhibits the PI3K/Akt pathway, and subsequently induces apoptosis in chicken splenic lymphocytes in vitro, and these effects are partially attenuated by Se supplementation. To the best of our knowledge, this study is the first to reveal the antagonistic effect of Se on Pb-induced apoptosis of chicken splenic lymphocytes in vitro via the activation of the PI3K/Akt pathway.

Fluoride-induced oxidative stress and apoptosis are involved in the reducing of oocytes development potential in mice

The present study was conducted to investigate the mechanisms of excessive-fluoride-induced reduction of oocyte development potential in mice. The development morphology of oocyte and the changes of pathomorphology in ovary were observed. The protein expression levels of apoptosis factors, including Bax, Bcl-2, casepase-3, casepase-9 and cytochrome c, and the mRNA expression levels of antioxidant enzymes, including SOD1, GSH-Px1, CAT and inducible nitric oxide synthase were measured by Western blot and real-time PCR, respectively. DNA damage in the ovary was analysed by single cell gel electrophoresis and TUNEL staining. Results indicated that the structure and function of ovarian cells were seriously damaged, followed, the development potential of oocyte was reduced by excessive fluoride. The expression levels of apoptosis factors were up-regulated and antioxidant enzymes were significantly down-regulated. Meanwhile, the contents of ROS, MDA, NO and iNOS were significantly increased. Whereas, the activities of SOD1, GSH-Px1 and CAT was significantly decreased compared with the control group. Simultaneously, the results of DNA analysis indicated that the tail length and tailing ratio of ovarian cells were significantly increased in the fluoride group. In summary, the results provided compelling evidence that excessive fluoride intake can reduce the development potential of oocyte by inducing oxidative stress and apoptosis in the ovary of female mice.

Carnosic acid induces apoptosis of hepatocellular carcinoma cells via ROS-mediated mitochondrial pathway

Carnosic acid (CA), an important bioactive phenolic diterpene mainly found in labiate plants, exerts various biological functions, including antioxidant, anti-inflammatory, antitumor, and neuroprotective activities. In the present study, we proved the deleterious effects of CA against hepatocellular carcinoma (HCC) in both in vitro and in vivo models. In vitro, CA significantly decreased cell viability, inhibited cell proliferation and migration, enhanced apoptosis, and increased caspase-3, -8, and -9 activities in HepG2 and SMMC-7721 cells. Specifically, CA led to a decreased mitochondrial membrane potential (MMP) and increases in intracellular reactive oxygen species (ROS) levels and apoptosis-related protein expression. Pre-incubation of HCC cells with N-Acetyl-l-cysteine (NAC), a ROS inhibitor, strongly suppressed CA-induced apoptotic phenomena, including reduced cell viability, excessive ROS levels, MMP decreases, and abnormal protein expression, suggesting an association of CA-induced apoptosis with oxidative stress-mediated mitochondrial pathways. In HepG2-and SMMC-7721-xenograft tumor mouse models, treatment with CA inhibited tumor growth and modulated apoptosis-related protein expression, confirming the anti-HCC effects of this chemical. Moreover, the CA-mediated anti-HCC effects associated with oxidative stress provide experimental evidence to support the potential use of CA as a drug therapy for HCC.

MiR-let-7a inhibits cell proliferation, migration, and invasion by down-regulating PKM2 in cervical cancer

In recent decades, miRNA has been reported as a crucial modulator in some biology progressions. This work aims to assess the expression and role of miR-let-7a and pyruvate kinase muscle isozyme M2 (PKM2) in CC tissues and cell lines. Here, we identified that miR-let-7a expression was decreased in CC tissues, and SiHa and HeLa cells (all P < 0.001), however, PKM2 expression was increased in these samples. Statistically, miR-let-7a was inversely associated with PKM2 mRNA or protein (p = 0.013, p = 0.015, respectively). In-vitro assays revealed that ectopic miR-let-7a expression repressed SiHa and HeLa cell proliferation, migration and invasion, and enhanced SiHa and HeLa cell apoptosis. Furthermore, luciferase reporter assays revealed the 3'-UTR of PKM2 was identified a target of miR-let-7a, by which miR-let-7a affected the expression of PKM2 in SiHa and HeLa cells. Besides, PKM2 plasmids partially abrogated the inhibitory effects of miR-let-7a, while si-PKM2 enhanced the inhibitory effects of miR-let-7a. In vivo, miR-let-7a mimics indeed repressed tumor growth in mice xenograft model. In conclusion, our results demonstrated that miR-let-7a inhibits cell proliferation, migration and invasion by down-regulation of PKM2 in cervical cancer. miR-let-7a/PKM2 pathway may be a useful therapeutic target for CC patients.

Carnosic Acid Suppresses the H2O2-Induced Mitochondria-Related Bioenergetics Disturbances and Redox Impairment in SH-SY5Y Cells: Role for Nrf2

The phenolic diterpene carnosic acid (CA, C₂₀H₂₈O₄) exerts antioxidant, anti-inflammatory, anti-apoptotic, and anti-cancer effects in mammalian cells. CA activates the nuclear factor erythroid 2-related factor 2 (Nrf2), among other signaling pathways, and restores cell viability in several in vitro and in vivo experimental models. We have previously reported that CA affords mitochondrial protection against various chemical challenges. However, it was not clear yet whether CA would prevent chemically induced impairment of the tricarboxylic acid cycle (TCA) function in mammalian cells. In the present work, we found that a pretreatment of human neuroblastoma SH-SY5Y cells with CA at 1 μM for 12 h prevented the hydrogen peroxide (H₂O₂)-induced impairment of the TCA enzymes (aconitase, α-ketoglutarate dehydrogenase (α-KGDH), succinate dehydrogenase (SDH)) and abolished the inhibition of the complexes I and V and restored the levels of ATP by a mechanism associated with Nrf2. CA also exhibited antioxidant abilities by enhancing the levels of reduced glutathione (GSH) and decreasing the content oxidative stress markers (cellular 8-oxo-2'-deoxyguanosine (8-oxo-dG), and mitochondrial malondialdehyde (MDA), protein carbonyl, and 3-nitrotyrosine). Silencing of Nrf2 by small interfering RNA (siRNA) abrogated the protective effects elicited by CA in mitochondria of SH-SY5Y cells. Therefore, CA prevented the H₂O₂-triggered mitochondrial impairment by an Nrf2-dependent mechanism. The specific role of Nrf2 in ameliorating the function of TCA enzymes function needs further research.